The present invention relates to digital signal processing, and more particularly to multi-channel audio output.
Balance in audio often refers to the ratio of loudness between two signals, typically right and left stereo channels. For instance many stereo hardware components have a knob labeled “balance” to control the loudness ratio of the two speakers. Automatic rebalancing refers to the automatic adjustment of an input signal to achieve nearly equal loudness levels at the outputs. This is useful in the case of, for instance, listening to poorly recorded or poorly mixed music, as is sometimes the case for old LPs, tapes and even CDs.
The basic goal of achieving balance can be attained by adjusting one channel to match the loudness of another. An additional worthwhile goal is to maintain the overall loudness, i.e. the rebalancing should not affect the overall perceived loudness. Another additional goal is to be robust against highly unbalanced signals. If one channel has a very low level, it might require a large increase in loudness, which can lift the noise floor and reduce the overall signal to noise ratio. Also, it may be the case that there is no signal at all on one of the channels. These are problems for known balancing methods.